Early Color Television
Butterfield Color Encoder
From the book Human Color Perception, by Joseph Sheppard, Jr:
One recent development is of particular interest. James Butterfield (168) has utilized the Prevost-Fechner-Benham Effect to obtain colored images on ordinary black-and white television receivers. The technique requires no modification in either transmission or reception. In use, a proprietary Color Encoder is attached to an ordinary black- and-white television camera lens. This Encoder uses the basic Prevost-Fechner-Benham sequence code based on Fig. 60. By referring to Fig. 60, one cycle of the Encoder may be analyzed in six successive frames as was done with Benhams Top. Frames 1, 2, and 3 are blank (opaque). Frame 4 presents the red primary image to the viewer by interspersing a cyan filter (the comple-mentary of red)* before the camera lens. (It was noted earlier that the object to be colored with the Prevost-Fechner-Benham should appear black on white surround.) Frame 5 presents the green primary image obtained through a magenta filter (the complementary of green).* Frame 6 presents the blue primary image obtained with a yellow filter (the complementary of blue).* This complete sequence is then repeated at the rate of 5 cps to be compatible with the domestic television framing rate of 30 frames/sec.
Two points must be emphasized concerning Butterfields technique. First, each of his primary images is a purely black-and-white image, since the television camera is simply an ordinary black-and-white camera. Second, the fact that the system works to give color summation via the three Prevost-Fechner-Benham primaries is apparently a new discovery. Composite hues (flesh tones, chocolate pudding) are formed with surprising fidelity, and they are actually more pleasing than the primaries, since the composites have less flicker. The flicker present in the technique is apparently its only serious drawback at present, but even this may be useful in some applications, such as commercials. Finally, it should be noted that Butterfields Color Encoder may be used in front of a live TV camera, or with a motion picture camera (black- and-white), or its effect may be dubbed by using an identical sequence of colored illuminants upon the scene to be shot. The actual filters used are proprietary information.
* Thus effectively blocking the corresponding color in the image.
Some commercials were produced using the technique and tested on a few television stations in the mid 60s. Here is an article about the system from the October, 1968 issue of Popular Electronics: